Tube around mesh wireframe
Starting in edit mode you want to delete all faces from the mesh object X.



Then convert the mesh to a curve &#9095; AltC



Now that you have a curve object you can add any bevel shape you want to it by editing a new curve object to the shape and set it as the bevel object.



As you may notice in that screenshot, the curve from mesh object may need some cleanup. A mesh object can branch out many time from one vertex where a curve is one continuous line, this can leave "loose ends" in the generated curve.